The electrodeposition and dissolution of zinc and amalgamated zinc in alkaline solutions

The reaction mechanism of zinc and amalgamated zinc was investigated with the galvanostatic transient technique in the concentration range 1.5–10 M KOH. The Tafel slopes of the zinc electrode were 40 mV anodically and 120 mV cathodically. The cathodic reaction order in zincate was found to be +1. From the Tafel slopes and the dependence of the exchange current density on the activity of the KOH, the reaction orders in OH− were calculated, yielding values of 2.3± 0.8 in the anodic and −0.8 ± 0.2 in the cathodic direction. These results are consistent with the suggested mechanism of Bockris et al.[16] for the zinc electrode. The Tafel slope in cathodic direction of the amalgamated zinc electrode was a function of the KOH concentration (120 mV at KOH concentrations up to 3 M; about 60 mV in 10 M KOH); the anodic Tafel slope was 30 mV over the whole concentration range. These results and measurements at constant ionic strength suggest a mechanism which involves the participation of water. The difference in behaviour of the zinc electrode and the amalgamated zinc electrode is probably caused by changes in the adsorption characteristics due to amalgamation.